The invention relates to ducts for routing engine cooling air to pneumatically blast dust, chaff and other debris off the top of an axial separator and associated drive mechanism. More specifically, the present invention related to placing an airfoil in the air-stream of such a duct for optimal performance.
In threshing a harvested crop, the grain is separated from straw and chaff and deposited into a holding tank. With conventional combines the harvested crop is directed to a transversely mounted threshing cylinder and concave, which threshes the crop, separating the grain from the straw. The residue is then directed to a beater further separating the grain from the straw. The straw residue is then passed over oscillating apertured straw walkers which direct the straw out of the back of the combine while allowing additional grain to fall through the apertures. Grain and chaff falling from the threshing concave and straw walkers is directed to a cleaning shoe for separating the chaff from the grain. A blower assembly is used in this final step to blow the lighter chaff away from the heavier grain. In a rotary combine, the grain is directed to a cylindrical tube housing a rotor. The harvested crop is threshed and separated in the cylindrical tube with the grain and chaff falling therefrom in a manner similar to the conventional combine.
A hybrid machine having a transverse threshing cylinder and a pair of axial separating units is disclosed in U.S. Pat. No. 4,739,773, which is incorporated herein by reference. The axial separating units comprise cylindrical tubes having rotors housed therein. It has been found that dust, chaff and other debris collects on the top of the axial separating units. It is known to provide an air duct that receives an air stream from a cooling system fan to blow debris off the top portion of an axial separator unit. Examples are disclosed in U.S. Pat. Nos. 5,088,960 and 6,468,153. It is desirable for such a duct to provide an air stream with sufficient volume and velocity to effectively blow debris from that area.
The present invention is directed to using engine cooling air to pneumatically blast dust, chaff and other debris off the top of the axial separator units and the linkage that drives the rotors of the axial separator units. Ductwork directs cooling air from the engine cooling system to the top of the axial separator and the rotor drive linkage. A deflector located above the separator divides the air into a forward component and a rearward component. An airfoil is placed near the inlet of the ductwork to help direct air toward the outlet and prevent air from recirculating back toward the inlet. Airflow through the ductwork is thereby enhanced.